The present invention relates generally to semi-submersible structures, and more particularly to the stabilization of such structures in heavy seas.
Semi-submersible platforms are required in various types of offshore operations, including scientific surveys, and oil and gas drilling and production. A platform typically comprises an elevated deck supported by a number of vertical columns which are often connected near the lower ends by horizontally extending pontoons. The platform floats with the lower portions of the vertical columns and the pontoons submerged and the deck above the water surface.
In use, a stable platform is desired. However, wave motion produces substantial undesirable platform displacement. In heavy seas, it is particularly desirable to reduce heave in order to achieve platform stability, heave being the vertical linear displacement of the platform which occurs in response to wave motion.
Improvements for stabilizing semi-submersible platforms are disclosed in copending U.S. patent application Ser. No. 649,997 filed Jan. 19, 1976, by Gunnar B. Bergman and assigned to the same assignee as the present invention. Said improvements operate to apply controlled damping forces to a platform, thereby to counteract the forces of wave motion which cause oscillatory platform displacement.
It is an object of the present invention to improve stabilization of semi-submersible platforms by providing pontoon configurations which act to reduce heave.